The present invention relates to cleaning a substrate.
In the manufacture of integrated circuits, active and passive devices are formed on a substrate, such as a semiconductor wafer, by alternately depositing and etching layers of dielectric, semiconducting, and conducting materials, such as silicon dioxide, polysilicon, and metal compounds and alloys. These layers may be etched to form a pattern of etched features by providing a resist layer of photoresist and/or oxide hard mask on the substrate, and using lithography or energized gas to expose and pattern the resist layer. The portions of the layers adjacent to the patterned resist features are etched to form a predefined pattern of gates, vias, contact holes, trenches, and/or metal interconnect lines. Etching is typically performed using a capacitively or inductively coupled plasma of halogen-containing gases, as for example described in Silicon Processing for the VLSI Era, Vol. 1, Chapter 16, by Wolf and Tauber, Lattice Press, 1986, which is incorporated herein by reference.
The etching process may leave remnant resist and etchant residue on the substrate. Remnant resist are those residual resist portions that are not etched by the etchant gases, and which remain on the substrate after the etching process. The etchant residue may comprise residual species and/or sidewall deposits on the sidewalls of the etched features. The residual species may result from adsorption of halogen-containing etchants on the etched features which may lead to corrosion of the metal-containing features. The sidewall deposits may be formed during the etching process by reaction of the etchant gases, the metal-containing layers, and the resist, and by condensation of the reaction residue on the sidewalls of the features. One method of cleaning an etched substrate is a dry cleaning method in which a plasma of a gas is used to remove remnant resist remaining on the substrate in a stripping (or ashing) process and to remove or inactivate residual halogen-containing species in a passivating process. The sidewall deposits on the substrate are typically removed by wet chemical etching methods or they can be at least partially removed in a dry cleaning process.
Conventional stripping methods which use a plasma of oxygen, nitrogen or water vapor, can be used to strip remnant resist from the substrate. These conventional stripping techniques are sometimes ineffective at stripping all the resist from the substrate, particularly when the polymeric resist is hardened by exposure to a plasma. For oxide hard mask resists, the oxide layer can be stripped or can be left on the substrate. Typically, remnant oxide hard mask is left on the substrate and a dielectric layer is deposited on the remnant oxide in a subsequent process step. In addition, adequate stripping processes generally compromise process throughput. The stripping process may also harden sidewall deposits making the deposits difficult to remove.
In passivating techniques, the etchant residue on the substrate is removed or inactivated to, for example, reduce post-etch corrosion problems by using a passivating gas, such as ammonia and/or water vapor. One limitation of conventional passivating techniques is that they often only prevent post-etch corrosion of the substrate for short periods, typically ranging from about 1 to 5 hours after exposure of the substrate to ambient moisture. The short corrosion resistant period is undesirable because post-etch processing steps may need to be performed within 1 to 2 hours after the substrate is first exposed to the atmosphere, resulting in a tight or inflexible production schedule. Often, the substrate cannot be etched, or if already etched, cannot be removed from the chamber in order to avoid corrosion.
Due to the shortcomings of the conventional dry cleaning processes, remnant resist and/or etchant residues are often removed in a wet-cleaning process in which the substrate is exposed to wet solvents. However, the wet-cleaning process also suffers from several disadvantages. For example, residue removal is often not complete, resulting in inconsistently processed substrates. In addition, the solvents may attack the metal-containing features on the substrate, particularly when very small features are etched on the substrate. The solvents used may also be costly and may generate hazardous chemical waste that is difficult to dispose of.
Thus, there is a need for a process and apparatus for cleaning a substrate to, for example, remove remnant resist and etchant residue on the substrate. It is further desirable to reduce post-etch corrosion. It is still further desirable to be able to clean a substrate while reducing the need to expose the substrate to a wet solvent.
The present invention satisfies these needs. In one aspect of the present invention, a substrate processing method comprises exposing a substrate to an energized process gas to etch the substrate, exposing the substrate to an energized cleaning gas, and before, during, or after exposing the substrate to an energized cleaning gas, exposing the substrate to an energized treating gas comprising a halogen species and a hydrogen species.
In another aspect of the invention, a substrate processing method comprises exposing a substrate to an energized process gas to etch the substrate and exposing the substrate to an energized treating gas comprising a chlorine species.
In another aspect of the invention, a substrate processing method comprises exposing a substrate to an energized process gas to etch the substrate and exposing the substrate to an energized treating gas comprising a fluorine species and a hydrogen species.
In another aspect of the invention, a method of treating an etched substrate comprises exposing the etched substrate to an energized process gas comprising a first halogen species and exposing the etched substrate to an energized process gas comprising a second halogen species.
In another aspect of the invention, a method of cleaning an etched substrate comprises exposing a substrate to a cleaning gas; and after this, exposing the substrate to an energized treating gas comprising one or more of NH3 and H2.
In another aspect of the invention, a substrate processing method comprises exposing a substrate to an energized process gas to etch the substrate in a process zone and exposing the substrate to an energized treating in the process zone.
In another aspect of the invention, a method of treating an etched substrate comprises exposing the etched substrate to an energized process gas comprising oxygen species while maintaining the substrate at a temperature of at least about 200xc2x0 C., treating the substrate with a treating gas and rinsing the substrate with de-ionized water to remove etchant residue on the substrate.